The sporty watch is, according to all the guides I've looked at, located at this canyon in Yaschas Massif 100AF. I've been there many times and tried everything: time reversal, blindly throwing Mog in, but the treasure box just isn't there! Its really annoying me coz if I get this one fragment from Yaschas Massif 10AF I can get 2 more fragment skills. I have finished the main story and a few paradox endings. Why isn't the treasure box there?
i believe it would be in 110af yaschas massif, from the ruins follow the path to the west(DO NOT GO SOUTH) till you see a canyon at you're right.